The present disclosure pertains to sealed floating roofs for storage tanks.
Above ground storage tanks are frequently used to store hydrocarbon fluids. Because the stored fluid (e.g., liquid, gas, liquid-gas mixtures) may be volatile, the storage tank is often equipped with a floating roof. Some storage tanks utilize a combination fixed roof and floating roof design. The floating roof may be a full-contact floating roof configured to move up and down with the fluid level in the tank. In other words, the floating roof makes contact with the fluid within the tank. As a result, air gaps between the roof and the fluid may be reduced, thereby reducing fluid evaporation and potentially decreasing losses of stored product.
Storage tanks may be designed with seals to prevent leakages or losses of product. For example, the storage tanks may be formed from roof panels that are bolted and/or riveted to an internal frame. Additionally, the roof panels may include sealing devices (e.g., polymers, metals, composite materials) to substantially isolate the environment from the interior of the tank. However, under certain conditions, the seals may degrade over time, thereby resulting in repairs and/or potential leakage points.
In order to reduce the likelihood of leakages, some storage tanks include welded connections between the roof panels. On such design, presented in U.S. patent application Ser. No. 12/642,270, which is hereby incorporated by reference, includes a roof panel having a sealed cavity. In such embodiments, a weld seam coupling a bottom plate to a frame member may be exposed to product within the tank. However, it may be desirable to provide a floating roof having weld seams that are substantially isolated from the product within the tank.